The present invention is directed to firearms which can be converted to fire simulated ammunition for training purposes, for example in military weapons like the M16 shoulder-mounted rifle, and the 9 mm semiautomatic Beretta handgun. The M16 automatic, or select-fire, rifle and the AR15 semiautomatic rifle have been the standard-issue weapons of the U.S. military and civilian police departments for decades. The rifle design was originally created by Eugene Stoner and developed by Fairchild Engine and Airplane Company in the 1950's. Modified versions of the M16 designated as the M16A1 and the M16A2 are currently in use by armed forces in the U.S. and throughout the world. A civilian semiautomatic version of the M16, designated as the AR15 is sold to civilians by Olympic Arms, Inc. of Olympia, Wash. When used herein, the phrase "M16" is intended to include all versions of the M16 and AR15 previously and currently being produced.
One of the original patents issued on the M16 rifle was issued to Eugene Stoner on Sep. 6, 1960, as U.S. Pat. No. 2,951,424, and disclosed the M16 bolt and bolt carrier system as well as the gas system used therewith. The patent discloses a rifle utilizing a gas tube that extends from a gas port in the barrel, through the front sight base, back into the receiver, and into a gas tube pocket or "gas key" attached to the bolt carrier. Stoner also received U.S. Pat. No. 3,198,076 on Aug. 3, 1965 which discloses a gas operated, magazine-fed rifle that can be readily converted to a belt-fed machine gun by inverting the barrel assembly.
More recently, patents have been issued on modified M16 rifles that are chambered for the relatively low-pressure, short wide pistol cartridges such as the 9 mm, the 10 mm, and the .40 S&W calibers. These cartridges generate approximately half the internal gas pressures that normal rifle cartridges such as the 5.56 mm Nato cartridge do. For example, the 9 mm generates pressures in the range of 20,000 to 30,000 CUP whereas modern military rifle cartridges generate pressures in the range of 45,000 to 55,000 CUP (copper units of pressure). Two such patents disclosing modified M16 rifles for firing pistol cartridges are U.S. Pat. No. 5,499,569 and U.S. Pat. No. 5,520,019, dated Mar. 19, 1996, and May 28, 1996, respectively, both issued to Brian D. Schuetz and assigned to the assignee of the present invention. Two other patents disclosing modified M16 rifles are U.S. Pat. No. 5,448,940 and U.S. Pat. No. 5,351,598, issued on Sep. 12, 1995, and Oct. 4, 1994, respectively, to Robert C. E. Schuetz et al. The aforementioned six patents issued to Stoner and Schuetz, et al, are all incorporated herein by reference in their entirety.
In the training of military troops and civilian police forces, the trainers are limited to the types of firearms that can be used in such training because of the inherent dangers in using live ammunition during training exercises. The alternatives to using live ammunition include using blanks in standard military weapons such as the M16 or using non-military pseudo-weapons such as CO2 operated rifles that shoot frangible projectiles made up of plastic capsules filled with a colored marking fluid such as watercolor paint (often referred to as "paintball guns"). The advantages of shooting blanks in actual military rifles is that the trainees actually get the feel of the weapon they will be carrying; however the disadvantage is that no one can tell how accurate the trainee is under training conditions because of the lack of projectiles with the blank cartridges. The alternative offers the opposite advantages and disadvantages, i.e. the CO2 guns do not resemble the military type of weapons in design, weight, handling and all other aspects, even though they do provide a projectile that allows some tracking of accuracy; although only at very limited distances because of the lack of velocity and distance with the CO2-driven frangible projectiles.
What has long been needed has been a system of firing simulated ammunition from weapons such as the M16 rifle and the 9 mm Beretta handgun which are standard-issue weapons in the U.S. military.